240 D. D. CUNNINGHAM, 
beginning to be emitted ere the entire disappearance of its pre- 
decessor. ‘he pseudopodia gradually diminish in size as time 
goes on and finally disappear, the last traces of their formation 
being represented by mere wave-like undulations of the body- 
margin. The flagella have been retracted some time previously, 
and the zoospore finally remains as a mere rounded or oval par- 
ticle of protoplasm, which rapidly breaks down into a molecular 
flake and disappears. 
The presence of zoospores is by no means confined to cho- 
leraic excreta. They certainly, as a rule, are present in such 
excreta in much larger amount and much greater activity than 
in other cases, but in many cases of intestinal disease of other 
nature they may readily be detected, and even in cases where no 
abnormal condition exists, they are very frequently present in 
small numbers. Although this is the case, they may readily 
escape observation, and this for several reasons. In the first 
place, they are frequently inactive ; and secondly, even where 
they are not so, the nature of the medium is such as to prevent 
their free movement. Moreover, they are so easily and prejudi- 
cially affected by changes in the medium, that the means 
employed to facilitate their detection very often defeat their own 
end. ‘Thus, the addition of water is in almost all cases enough 
almost immediately to secure the abolition of motion, and very 
rapidly to lead to disintegration and disappearance of the zoo- 
spores. The two media which I have found most adapted to 
secure the demonstration of their presence are, first, the alkaline 
fluid of choleraic excreta; and second, a solution of cow dung. 
In either case, before using the media, it is of course necessary 
to filter and boil them in order to exclude débris and organisms 
which they may contain. In my first observations I always 
employed the choleraic fluid, but latterly I have entirely aban- 
doned this in favour of the solution of cow dung, which seems 
to be peculiarly favorable to the zoospores. 
The presence of the zoospores in the excreta is then a pheno- 
menon not peculiar to cholera, or indeed to any diseased con- 
dition. On the other hand, certain diseased conditions of the 
excreta appear certainly to be incompatible with their presence. 
As I previously pointed out,! cases of acid diarrhoea associated 
with the presence of growing fungal elements are characterised 
by the absence of any traces of the zoospores. This in itself is 
sufficient to show that mere fluidity of the medium is not the 
only condition necessary for the occurrence of these organisms. 
That this is the case is also proved by their entire absence in 
many cases of dysentery. A much more important determinant 
1 Appendix B, ‘Seventh Annual Report of the Sanitary Commissioner 
with the Government of India,’ Calcutta, 1871. 
